Design and development of microstrip array antenna for wide dual band operation
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Design and development of microstrip array antenna for wide dual band operation

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Design and development of microstrip array antenna for wide dual band operation Design and development of microstrip array antenna for wide dual band operation Document Transcript

  • International Journal of Electronics and Communication Technology (IJECET), International Journal of Electronics and Communication Engineering &Engineering6464(Print), ISSN 0976 – 6472(Online) Volume 1, Number 1, Sep - Oct (2010), © IAEME ISSN 0976 – & Technology (IJECET) IJECETISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online)Volume 1, Number 1, Sep - Oct (2010), pp. 107-116 ©IAEME© IAEME, http://www.iaeme.com/ijecet.html DESIGN AND DEVELOPMENT OF MICROSTRIP ARRAY ANTENNA FOR WIDE DUAL BAND OPERATION Gangadhar P Maddani Department of PG Studies and Research in Applied Electronics Gulbarga University, Gulbarga E-Mail: gangadharmaddani@rediffmail.com Sameena N Mahagavin Department of PG Studies and Research in Applied Electronics Gulbarga University, Gulbarga E-Mail: sameena.nm@rediffmail.com Shivasharanappa N Mulgi Department of PG Studies and Research in Applied Electronics Gulbarga University, Gulbarga E-Mail: s.mulgi@rediffmail.com ABSTRACT This paper presents a novel design of slot loaded two elements rectangular microstrip array antenna (SRMAA) for triple band operation. If the ground plane of SRMAA is minimized to 48.8% by removing the copper layer on either side of vertical axis of the substrate from the centre, converts triple-band in to dual-bands. Further, by reducing the ground plane to 76.8%, the antenna enhances impedance bandwidth of each operating band in the dual band operation and gives maximum 40.1% and 50% of impedance bandwidth and enhances the gain from 2.07 to 3.73dB without changing much the nature of omni directional radiation characteristics. The proposed antennas are simple in their geometry and are fabricated using low cost glass epoxy substrate material. These antennas may find applications for the microwave communication systems operating at IEEE 802.11a (5.15 – 5.35GHz), HIPERLAN/2 (5.725 – 5.825GHz) and X (8 – 12.5GHz) band of frequencies. Details of antenna design are described and experimental results are discussed. Keywords: microstrip antenna, array antenna, dual-band, omni directional. 107
  • International Journal of Electronics and Communication Engineering & Technology (IJECET),ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 1, Number 1, Sep - Oct (2010), © IAEME1. INTRODUCTION In recent years, the use and considerable interest in microstrip antennas (MSAs)has become wide spread because of its significant merits of small size, light weight, low-profile, low cost and direct integrability with microwave circuits. However, one of theserious limitations of MSAs is their narrow impedance bandwidth and lower gain.Several promising techniques are available in the literature for the enhancement ofimpedance bandwidth and gain such as use of stacked configuration [1], additionalresonator [2], aperture coupling [3], parasitic patch [4], etc. But these methods requirethick substrate and also increase the area of the antenna. Further, dual or triple band antennas have gained wide attention in manymicrowave communication systems because they avoid the use of separate antennas fortransmit/receive applications for each operating band, particularly in synthetic apertureradar (SAR) [5]. Various techniques are available in the literature to achieve dual bandoperation [6-7]. In this study, a simple slot loaded array technique has been used toachieve triple band operation. To convert triple band into dual band, the ground plane isminimized. The enhancement of impedance bandwidth at each operating band and gain isachieved by using optimum ground plane of the array configuration without changing thenature of radiation characteristics. This kind of study is rarely found in the literature.2. DESCRIPTION OF ANTENNA GEOMETRY Figure 1 Geometry of SRMAA The proposed antennas are designed using low cost glass epoxy substrate materialof thickness h = 0.16 cm, permittivity εr = 4.2 and area = A×B. The artwork of the 108
  • International Journal of Electronics and Communication Engineering & Technology (IJECET),ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 1, Number 1, Sep - Oct (2010), © IAEMEproposed antennas is sketched using computer software Auto-CAD 2006 to achievebetter accuracy. The antennas are fabricated using photolithography process. Figure 1 shows the top view geometry of slot loaded two element rectangularmicrostrip array antenna (SRMAA). The length L and width W of the patch is designedfor resonant frequency of 5GHz, using the equations available in the literature for designof rectangular patch [8]. The rectangular slots are placed at the centre along the length Lof upper non radiating edge of the patch. The half U shaped slots are placed inside thepatch from bottom non radiating edge L at a distance of 1mm. The dimensions of slotsare taken in terms of λo, where λo is free space wavelength in cm. The length LR andwidth WR of rectangular slot is taken as λo/8.57 and λo/60 respectively. The dimensionsof half U shaped slot having horizontal length LH and vertical length LV are taken asλo/30 and λo/8 respectively. The distance D between the two radiating elements fromtheir centre should be λo/2 for minimum side lobes [9]. But in Fig. 1, D is taken asλo/2.33 in order to keep the feed line as compact as possible for minimum feed line loss.Further, when D is less than λo/2.33; it becomes difficult to accommodate the feedarrangement between the array elements. Hence D = λo/2.33 is treated as optimum in thiscase. The parallel feed arrangement has wideband performance over series feed andhence selected in this case to excite the array elements of Figure 1. The feed arrangementshown in Figure 1 is a contact feed and has advantage that it can be etchedsimultaneously along with antenna elements. The parallel feed arrangement of Figure 1consists of a 50 microstripline feed of length L50 and width W50 is connected to 100microstripline feed of length L100 and width W100 to form a two way power divider. A100 quarter wave matching transformer of length Lt and width Wt is connected between100 microstripline feed and mid point of the radiating elements in order to ensureperfect impedance matching. The bottom plane of SRMAA is tight ground plane coppershielding. The ground plane shielding of SRMAA is minimized to 48.8% with respect toground plane area A×B as shown in Figure 2 retaining its top geometry. This antenna isnamed as modified ground plane slot loaded two elements rectangular microstrip arrayantenna (MRMAA). The size of copper area on the ground plane is taken as A1×B.Figure 3 shows the bottom view geometry of large modified ground plane slot loaded two 109
  • International Journal of Electronics and Communication Engineering & Technology (IJECET),ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 1, Number 1, Sep - Oct (2010), © IAEMEelements rectangular microstrip array antenna (LRMAA). The size of copper area on theground plane is taken as A2×B which is 76.8% smaller than the area A×B retaining its topgeometry same as that of Figure 1. The various parameters of proposed antennas aregiven in Table 1. Figure 2 Ground plane geometry of MRMAA Figure 3 Ground plane geometry of LRMAA Table 1 Design Parameters of Proposed Antennas Antenna Dimensions Antenna Dimensions Parameters (cm) Parameters (cm) A 5.00 L100 0.38 B 3.50 W100 0.07 L 1.41 D 2.56 W 1.86 A1 2.56 Lt 0.38 A2 1.16 Wt 0.015 LR 0.70 L50 1.54 WR 0.10 W50 0.32 LH 0.20 λ0 6.00 LV 0.75 110
  • International Journal of Electronics and Communication Engineering & Technology (IJECET),ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 1, Number 1, Sep - Oct (2010), © IAEME3. EXPERIMENTAL RESULTS The impedance bandwidth over return loss less than −10dB of the proposedantennas is measured on Vector Network Analyzer (Rohde & Schwarz, Germany makeZVK model 1127.8651). The variation of return loss versus frequency of SRMAA is asshown in Figure 4. From this figure, it can be seen that, the antenna resonates for threebands of frequencies BW1, BW2 and BW3.The impedance bandwidth (BW) at eachoperating band is determined by using the equation,  (f − f )  BW =  2 1  ×100 %  fc  Where, f1 and f2 are the lower and upper cut-off frequencies of the bandrespectively, when its return loss becomes −10dB and fc is the center frequency betweenf1 and f2. The magnitude of each operating band BW1, BW2 and BW3 in Figure 4 is foundto be 10.2, 11.7 and 20.64% respectively. The triple bands are due to the independentresonance of radiating elements and slots on SRMAA. Figure 4 Variation of return loss verses frequency of SRMAA The variation of return loss versus frequency of MRMAA is as shown in Figure 5.From this graph, it can be observed that, the antenna resonates for dual band offrequencies BW4 and BW5 with corresponding magnitudes of impedance bandwidth is12.1 and 47% respectively. Further, from this figure, it is clear that the two bands BW1and BW2 of Figure 4 merges into a single band BW4 as shown in Figure 5. This is due to 111
  • International Journal of Electronics and Communication Engineering & Technology (IJECET),ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 1, Number 1, Sep - Oct (2010), © IAEMEthe effect of reduction of ground plane in MRMAA. However, the bandwidth BW3 shownin Figure 4 enhances from 20.64% to 47% i.e. BW5 which is evident from Figure 5.Hence, by modifying the ground plane geometry of SRMAA triple band operation can beconverted into dual band operation with enhanced upper band BW5. Figure 6 shows thevariation of return loss versus frequency of LRMAA. The antenna resonates again fordual bands BW6 and BW7 and gives maximum impedance bandwidth at each operatingband i.e. BW6 and BW7. The magnitudes of impedance bandwidths of BW6 and BW7 arefound to be 40.1% and 50% respectively. These bandwidths are 94.28% and 6.38% morewhen compared to the impedance bandwidths BW4 and BW5 respectively. Theenhancement of impedance bandwidth of LRMAA is due to the effect of reduced groundplane. This reduced or optimum ground plane acting as secondary slot. The surfacecurrent around the secondary slot perimeter increases the electrical length which accountfor decrease in resonant frequency. Hence the patch and slot on the patch resonates closeto each other resulting in enhancement of impedance bandwidth [10]. Figure 5 Variation of return loss verses frequency of MRMAA The radiation patterns of proposed antennas i.e. antennas under test (AUT) aremeasured by connecting a standard pyramidal horn antenna in far field region. The AUTis connected in receiving mode and is kept in phase with respect to transmittingpyramidal horn antenna. The power received by AUT is measured from 00 to 3600 with 112
  • International Journal of Electronics and Communication Engineering & Technology (IJECET),ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 1, Number 1, Sep - Oct (2010), © IAEMEsteps of 100. The typical radiation patterns of SRMAA, MRMAA and LRMAA aremeasured at 8.5, 7.56 and 4.48GHz respectively. These are shown respectively in Figure7, 8 and 9. From these figures, it is observed that the patterns are omni directional innature. Hence the reduction of ground plane does not affect much on the nature ofradiation characteristics but enhances the impedance bandwidth at each operating band inthe dual band operation. Figure 6 Variation of return loss verses frequency of LRMAA Figure 7 Radiation pattern of SRMAA measured at 8.5GHz 113
  • International Journal of Electronics and Communication Engineering & Technology (IJECET),ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 1, Number 1, Sep - Oct (2010), © IAEME Figure 8 Radiation pattern of MRMAA measured at 7.56GHz Figure 9 Radiation pattern of LRMAA measured at 4.48GHz For the calculation of gain of proposed antennas, the power transmitted Pt bypyramidal horn antenna and power received Pr by AUT is measured independently. Withthe help of these experimental data, the gain G (dB) of AUT is calculated using theabsolute gain method [9],  Pr   λ0  ( G ) dB=10 log   − ( Gt ) dB − 20 log   dB  Pt   4πR  114
  • International Journal of Electronics and Communication Engineering & Technology (IJECET),ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 1, Number 1, Sep - Oct (2010), © IAEME Where, Gt is the gain of the pyramidal horn antenna and R is the distance betweenthe transmitting antenna and the AUT. The maximum gain of SRMAA, MRMAA andLRMAA are found to be 2.07, 3.65, and 3.73dB respectively. Hence LRMAA giveshighest gain among the proposed antennas.4. CONCLUSION From the detailed experimental study, it is concluded that triple band operationwith omni directional radiation pattern of antenna is achieved by designing SRMAA. Byreducing area of the ground plane by 48.8% with respect to the ground plane area ofSRMAA, triple band operation can be converted into dual band operation. Further, if theground plane area of SRMAA is reduced to 76.8% the maximum enhancement ofimpedance bandwidth at each operating band in the dual band operation is possiblewithout much changing the nature of omni directional radiation characteristics. Thistechnique also enhances the gain from 2.07 to 3.73dB. The proposed antennas are simplein their design, fabrication and they use low cost substrate material. These antennas mayfind applications for microwave communication systems operating at IEEE802.11a (5.15– 5.35GHz), HIPERLAN/2 (5.725 – 5.825GHz) and X (8 – 12.5GHz) band offrequencies.ACKNOWLEDGEMENTS The authors would like to thank the authorities of Dept. of Sc. & Tech. (DST),Govt. of India, New Delhi, for sanctioning Network Analyzer to this Department underFIST project.REFERENCES 1. Zehforoosh .Y., et. al. (2006), “Antenna design for ultra wide band application using a new multilayer structure”, PIERS online, Vol.2, No.6, pp.544-549. 2. Kumar .G and Gupta K.C (1984), “Broad-band microstrip antennas using additional resonators gap-coupled to the radiating edges”, IEEE Trans Antennas Propag, Vol. 32, No.12, pp.1375-1379. 3. Jazi .M.N., et. al. (2008), “Design and implantation of aperture coupled microstrip IFF antenna”, PIERS online, Vol.4, No.1, pp.1-5. 115
  • International Journal of Electronics and Communication Engineering & Technology (IJECET),ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 1, Number 1, Sep - Oct (2010), © IAEME 4. Nishiyama .E. and M. Aikawa (2004), “Wide-band and high gain microstrip antenna with thick parasitic patch substrate”, IEEE Antennas and Propag, Soc. Inter. Symp, Vol.1, pp.273-276. 5. Wang .W., et. al. (2004), “A dual polarized stacked microstrip antenna sub array for X-band SAR application”, IEEE Antennas and Propag, Soc. Inter. Symp, Vol.2, pp.1603-1606. 6. Jui Han Lu (1999), “Single feed dual frequency rectangular microstrip antennas with pair of step slots”, Electron Lett, Vol.35, No.5, pp.354-355. 7. Shun-Yun Lin and Kin-Lu Wong (2001), “A dual frequency microstrip line fed printed slot antennas”, Microwave Opt Technol Lett, Vol. 28, No.6, pp.373-375. 8. I. J. Bhal and P. Bhartia (1981), “Microstrip Antennas”, Artech House, New Delhi. 9. C. A. Balanis (1982), “Antenna Theory Analysis and Design”, John Wiley & Sons, New York. 10. Wang .H.Y., and Lancaster .M.J (1999), “Aperture-coupled thin film superconducting mender antennas”, IEEE Trans Antennas Propag, Vol. 47, No.5, pp.829-836. 116